1. Field of the Invention
The present invention relates to a wide-band receiving apparatus, and more particularly to a wide-band receiving apparatus used in an FM(Frequency Modulaton)-FDM(Frequency Division Multiplex) type optical image distributing system for transmitting multi-wave and multiple TV signals.
2. Description of the Related Art
An FM-FDM type optical image distributing system is currently more greatly studied than an FDM type distributing system, because the former system has lower noise and lower distortion than the latter system and can transmit signals on a multi-channel basis. Most of the current research, however, concerns optimization of an optical modulating and demodulating system or an optical transmitting system as described in "Study on an optical image distributing system" published in the National Conference Autumn 1990, B-714, the Institute of Electronic Information and Communication Engineers in Japan.
On the other hand, a wide-band receiving front-end apparatus is disclosed in "Trial Manufacture of an Optical Image Distributing Tuner" published in the National Conference, spring 1991, B-917, the Institute of Electronic Information and Communication Engineers in Japan. This front-end apparatus operates to select a desired signal from an optical demodulating signal ranging from 57.54 MHz to 1668 MHz and demodulate the selected signal.
Each of the foregoing wide-band receiving apparatuses needs a front-end device having two mixers and a local oscillating circuit. Hence, it is disadvantageous in that the apparatus is complicated in arrangement and is expensive.